62 lines
1.8 KiB
Diff
62 lines
1.8 KiB
Diff
2006-12-22 Paul Eggert <eggert@cs.ucla.edu>
|
|
|
|
* lib/autoconf/functions.m4 (AC_FUNC_MKTIME):
|
|
Include <limits.h>, and use its INT_MAX to rewrite the
|
|
j loop so that it does not overflow 'int'. Problem reported by
|
|
Ralf Wildenhues in
|
|
<http://lists.gnu.org/archive/html/bug-gnulib/2006-12/msg00084.html>.
|
|
Play it safe by shifting left by 1 rather than multiplying by 2,
|
|
as GCC is less likely to optimize this away when the value
|
|
is signed (when it assumes overflow leads to undefined behavior).
|
|
Also, don't assume time_t uses two's complement.
|
|
|
|
diff --git a/lib/autoconf/functions.m4 b/lib/autoconf/functions.m4
|
|
index 185376e..a34c9f0 100644
|
|
--- a/lib/autoconf/functions.m4
|
|
+++ b/lib/autoconf/functions.m4
|
|
@@ -984,6 +984,7 @@ AC_CACHE_CHECK([for working mktime], ac_cv_func_working_mktime,
|
|
# endif
|
|
#endif
|
|
|
|
+#include <limits.h>
|
|
#include <stdlib.h>
|
|
|
|
#ifdef HAVE_UNISTD_H
|
|
@@ -1132,12 +1133,15 @@ main ()
|
|
isn't worth using anyway. */
|
|
alarm (60);
|
|
|
|
- for (time_t_max = 1; 0 < time_t_max; time_t_max *= 2)
|
|
- continue;
|
|
- time_t_max--;
|
|
- if ((time_t) -1 < 0)
|
|
- for (time_t_min = -1; (time_t) (time_t_min * 2) < 0; time_t_min *= 2)
|
|
- continue;
|
|
+ for (;;)
|
|
+ {
|
|
+ t = (time_t_max << 1) + 1;
|
|
+ if (t <= time_t_max)
|
|
+ break;
|
|
+ time_t_max = t;
|
|
+ }
|
|
+ time_t_min = - ((time_t) ~ (time_t) 0 == (time_t) -1) - time_t_max;
|
|
+
|
|
delta = time_t_max / 997; /* a suitable prime number */
|
|
for (i = 0; i < N_STRINGS; i++)
|
|
{
|
|
@@ -1152,10 +1156,12 @@ main ()
|
|
&& mktime_test ((time_t) (60 * 60 * 24))))
|
|
return 1;
|
|
|
|
- for (j = 1; 0 < j; j *= 2)
|
|
+ for (j = 1; ; j <<= 1)
|
|
if (! bigtime_test (j))
|
|
return 1;
|
|
- if (! bigtime_test (j - 1))
|
|
+ else if (INT_MAX / 2 < j)
|
|
+ break;
|
|
+ if (! bigtime_test (INT_MAX))
|
|
return 1;
|
|
}
|
|
return ! (irix_6_4_bug () && spring_forward_gap () && year_2050_test ());
|